There are conventional techniques that improve fuel economy of vehicles by reducing rolling resistance of tires (i.e., by improving the rolling resistance performance). Today, however, there is an increasingly growing demand for higher fuel economy of vehicles. With this demand has come a demand for a rubber composition having excellent performance in terms of low heat build-up (excellent fuel economy) which is used for preparing a tread which is a tire component occupying a large portion of a tire compared with other tire components.
A known method for providing a rubber composition with sufficiently low heat build-up is to reduce the amount of reinforcing filler in the rubber composition. In this case, however, the hardness of the rubber composition is decreased and thus tires produced therefrom are softer. Such tires may disadvantageously impair vehicle steering performance (handling stability) and exhibit low wet grip performance and low abrasion resistance.
Patent Literature 1 teaches that the use of a modified styrene-butadiene rubber, which has been modified with a certain organic silicon compound containing an alkoxy group, enables improved fuel economy, wet grip performance, and abrasion resistance. However, in order to achieve satisfactory levels of all of these properties, further improvements are needed. Moreover, the modified styrene-butadiene rubber used has only one chain end modified, and modification of both chain ends or modification of two or more chain ends is not considered.